Plastic injection molding (PIM) is a manufacturing technology to plastic products, and it is important to determine optimal process parameters for high product quality and high productivity. Weldline that are formed when two or more melt fronts meet should be reduced for high strength and high surface quality. Rapid heating cycle molding (RHCM) that the mold is heated up is an attracted PIM technology for weldline reduction, but long cycle time is generally required. In this paper, an RHCM incorporating a heater system is used, and the process parameters optimization is performed. To determine the optimal process parameters, multi-objective optimization for minimizing both weldline and cycle time is considered. The numerical simulation in RHCM is computationally so expensive that sequential approximate optimization that the response surface is repeatedly constructed and optimized is adopted for the design optimization. The pareto-frontier is identified through the numerical simulation, and the experiment using PIM machine (MS100, Sodick) is also conducted. It is found from the numerical and experimental result that the RHCM using the heater system is effective to the weldline reduction.
In plastic injection molding (PIM), weldline affects the strength and surface quality of products, and it is then important to determine the optimal process parameters for the weldline reduction. Rapid heat cycle molding (RHCM) that actively controls the mold temperatures is an effective PIM technology to weldline reduction, but requires long cycle time. In this paper, variable pressure profile that packing pressure varies during the PIM process is incorporated in the RHCM in order to shorten the cycle time. To determine the process parameters in the proposed RHCM, multi-objective design optimization is performed. The mold temperature is maximized for the weldline reduction, whereas the cycle time is minimized for high productivity. Numerical simulation in the proposed RHCM is computationally so expensive that sequential approximate optimization is used to identify the pareto-frontier. Based on the numerical result, the experiment using PIM machine (MS100, Sodick) is also conducted to examine the validity of the proposed RHCM.
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